The purpose of the work is to study the mechanisms of gonadal sex differentiation and the interactions of the cells responsible for the development of the gonad. One possible regulator of gonadal differentiation is H-Y antigen, the genetics and biological significance of which need to be delineated more clearly, we are studying the genetics of H-Y antigen expression in a group of patients with gonadal dysgenesis. A standard H-Y antigen assay has been established and is being used to characterize the H-Y antigen of specific cell types. Two unusual findings have emerged from our work. The first is that there are many patients with gonadal dysgenesis who do not have a Y chromosome but do have H-Y antigen. (Many of these patients have mosaic cell lines.) The second is that most of the patients with gonadal dysgenesis and a Y chromosome who develop gonadal tumors have H-Y antigen. The location of the structural gene for H-Y antigen, which was once thought to be on the Y chromosome, therefore, needs to be redetermined, and the role of H-Y antigen is gonadal differentiation and the development of gonadal tumors needs to be reevaluated. In our study we are following a series of patients with gonadal dysgenesis typing of all them with respect to H-Y antigen. In order to be able to assess the function of H-Y antigen expression, a more precise H-Y antigen assay is being developed by raising monoclonal antibodies to the antigen. To study variations in H-Y antigen, we plan to use the monoclonal antibodies to delineate possible polymorphisms of H-Y antigen that may constitute the etiology of the pathology that we observe. We are carefully monitoring our patients with ultrasound examination for evidence of gonadal tumor formation. In addition, we are trying to develop a more reliable assay for H-Y antigen by raising monoclonal antibodies specific for H-Y antigen. The influence of germ cell differentiation and somatic genital ridge cells on gonadal development will be examined. Mosaic cell lines are being studied by producing tetraparental mice experimentally (including mosaic animals) and by using in vitro tissue culture techniques.